# Marpa, A practical general parser: the recognizer

arXiv: https://arxiv.org/abs/1910.08129 · HTML: https://mlsanity.com/paper/1910.08129/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 17 Oct 2019.

## Built on by (most cited first, 1 of 1)

- [Prefix Parsing is Just Parsing](https://mlsanity.com/paper/2604.21191/) (2026)

## Abstract (arXiv)

The Marpa recognizer is described. Marpa is a practical and fully implemented algorithm for the recognition, parsing and evaluation of context-free grammars. The Marpa recognizer is the first to unite the improvements to Earley's algorithm found in Joop Leo's 1991 paper to those in Aycock and Horspool's 2002 paper. Marpa tracks the full state of the parse, at it proceeds, in a form convenient for the application. This greatly improves error detection and enables event-driven parsing. One such technique is "Ruby Slippers" parsing, in which the input is altered in response to the parser's expectations.